One class of dispensers of cosmetic fluids, including in particular deodorants and antiperspirants is commonly called a roll-on dispenser or applicator. In such dispensers, a bottle or reservoir has an outlet aperture which is shaped to form a housing for a rotatable roller, commonly a ball, which conventionally is spherical. The roller is retained by the housing, having a fraction of its surface in fluid connection with the reservoir or bottle and a further fraction of its surface exposed outside the housing. In use, the roller can rotate within the housing, thereby conveying liquid from within the reservoir to outside the housing where it can be brought into contact with skin (or some other chosen surface). Although in some instances the housing is integral with the reservoir or bottle, it is often formed as a separate unit which is attached to the bottle by a suitable means, such as co-operating screw threads, or co-operating snap-fit beads on the respective contact surfaces of the housing and bottle.
Many users adopt similar applications habits, which is to say that they employ a similar number of strokes of the roll-on across the surface to which they are applying liquid, for example applying an antiperspirant or deodorant to the underarm or feet or other occluded body regions. Also they tend to use the dispenser for a similar length of time and it is believed that they seek to employ a similar application pressure between the dispenser and the skin, a pressure which enables the roll-on ball to roll over the skin surface rather than dig into it and/or slip. One problem that can arise with roll-on dispensers is that of controlling the amount of liquid that is applied, for example onto human skin by a user, or rather the lack of means in the dispenser itself to assist the user to apply a similar amount when adopting his or her normal application habit.
One adaptation proposed for roll-on housings comprises employing an intermediate reservoir between the main reservoir and the roller, a reserve which the roller can dip into on rotation and thereby replenish liquid that has been transferred onto the contacted surface, such as skin. Intermediate reservoirs are disclosed in for example U.S. Pat. No. 2,858,558, U.S. Pat. No. 3,111,703, GB-A-1115861, DE-A-19827965, DE 20119329A, DE 29914452, U.S. Pat. No. 3,075,230, U.S. Pat. No. 3,069,718, U.S. Pat. No. 3,284,839, U.S. Pat. No. 6,155,736, U.S. Pat. No. 6,179,505, WO-A-02/051283, GB 2268912A, and GB-A-2255052 amongst others, the roller being in the form of a ball or a cylindrical roller. However, the provision of an intermediate reservoir does not in itself regulate the depth of film adhering to the roller, but simply enables the fluid to be replenished.
An allied problem which can arise with roll-on dispensers is that of variation of the dose of fluid applied to the skin when applied by the user in the same application habit during the lifetime of the roll-on. It has been observed during a dosing study that after a start-up period, the dose applied from a current upright roll-on applicator can fluctuate significantly between successive applications, and that after about half of the dispenser contents has been applied, the average dose applied tends to diminish slowly whilst continuing to fluctuate between successive doses. This reduction in the dose may not be detected by the user, when following their regular application habit, for example taking a similar length of time and applying a similar number of application strokes. Thus, the efficacy of the dose can vary during the lifetime of the dispenser without being recognised by the user. It would be inherently advantageous for the dispenser to extend the proportion of cosmetic dispensed before tailing off commences and also advantageous to reduce the extent of fluctuation between successive doses.
A different type of adaptation to a roll-on housing for a bottle has been proposed in U.S. Pat. No. 2,968,826 which comprised a cylindrical housing having an integrally moulded resilient lateral spider (18) at its inward end, that is to say the end fitting into the bottle (10), and a ball-retaining lip (20) at its outward end against which a ball (27) was said to be normally forced by the spider (18) to seal the bottle. When the roll-on is rolled across the skin, '826 states that the ball was urged away from the lip thereby creating a narrow passage through which liquid could pass. However, in practice, the force needed to seal a ball against a housing is rather high, conventionally in the region of at least 3 kg-f, such as 4 to 8 kg-f, so that it would be very difficult for a user to operate a roll-on dispenser against a spider exerting such a ball-sealing force.
The dispenser of '826 has other disadvantages. Because the spider has a lateral surface facing the ball rather than a concave surface and a central button that contacts the ball, the height of the button does not control the rate of flow of liquid out of the dispenser or the film of liquid on the roll ball. Moreover, the gap between the lip of the ball during use of the roll-on to apply fluid is dependent on the pressure which the user exerts to overcome the outward bias of the spider. Inevitably, this gap is variable as a consequence, not only between users who are likely to exert different pressures from one another, but also during applications, especially in armpits where the angle of the hand changes during application as the roll-on follows the skin surface.
A housing for a roll-ball having an integrally moulded spider at its inward end is also described in DE 10211483. From the drawings, the ball-facing surface of the spider appears to have the same radius of curvature as the ball, which is patterned like a golf ball. The dispenser is sealed by an inner wall of the cap being forced against the exterior of the housing adjacent to its outward end. There is no suggestion of the spider having a means to control the gap between itself and the ball during dose application so as to regulate the depth of film on the ball.
In U.S. Pat. No. 5,213,431, there is described a roller dispenser in which beneath the cylindrical roller there is disposed an arcuate tray on the upper surface of which is moulded four ridges along substantially its entire length. The ridges are in contact with the length of the roller surface during its rotation whilst the dispenser is in use, not spaced from it. Accordingly, such ridges cannot provide a regulated depth of film, but serve to divide the tray into several reservoirs rather than one.
In GB 1515078, there is described a dispenser in which a transverse annular ring is spaced from a roll ball by three spacers, that prevent the ball from sealing against the ring and provide a passage for fluid. The top and side of the ring both present an acute angle to the ball tangent. Likewise, the interior of the ball housing is provided with three lugs 20 which prevent the ball from sealing against the housing wall when the dispenser cap is applied and likewise ensure a passage for fluid within the housing. The dispenser has moulded plastic spring members that are intended to press the ball against the lip of the housing, but as explained above with regard to U.S. Pat. No. 2,968,826 if the spring is sufficiently strong to provide sealing against the rim of the housing, it will be so strong as to require excessive force to be applied the user pushing the ball against a readily deformable skin surface. Likewise, such a system is not practicable for use in respect of fluid products for contact dispensing to the under-arm, and especially if the dispenser is an invert dispenser, namely one that it is normally stored with the ball and cap at its base underneath its reservoir.
It is an object of the present invention to ameliorate one or more of the disadvantages of roll-on housings for cosmetic roll-on dispensers indicated hereinbefore.
It is a further or alternative object of at least some embodiments of the present invention to provide a housing for a cosmetic roll-on dispenser having a means for controlling the liquid adhering to the roller for application onto a contact surface, such as skin.
It is a different or complementary object of at least certain embodiments of the present invention to provide a housing for the roller of a cosmetic roll-on dispenser that is particularly suited to an invert dispenser.